Terminal device, infrastructure equipment and methods for resource selection and updating of access class information

ABSTRACT

A terminal device for use with a wireless telecommunications network includes a transceiver configured to receive information indicative of one or more access classes of terminal devices which are permitted to exchange signals with the wireless telecommunications network, and a controller configured to update, the received information to modify the one or more access classes of terminal devices which are permitted to exchange signals with the mobile telecommunications network, the received information being updated by the controller according to a predetermined function of time.

BACKGROUND Field of Disclosure

The present disclosure relates to a terminal device, infrastructureequipment and methods.

Description of Related Art

The “background” description provided herein is for the purpose ofgenerally presenting the context of the disclosure. Work of thepresently named inventors, to the extent it is described in thisbackground section, as well as aspects of the description which may nototherwise qualify as prior art at the time of filing, are neitherexpressly or impliedly admitted as prior art against the presentinvention.

Third and fourth generation wireless communications systems, such asthose based on the third generation project partnership (3GPP) definedUniversal Mobile Telecommunications System (UMTS) and Long TermEvolution (LTE) architecture are able to support sophisticated servicessuch as instant messaging, video calls as well as high speed internetaccess. For example, with the improved radio interface and enhanced datarates provided by LTE systems, a user is able to enjoy high data rateapplications such as mobile video streaming and mobile videoconferencing that would previously only have been available via a fixedline data connection. The demand to deploy third and fourth generationnetworks is therefore strong and the coverage area of these networks,i.e. geographic locations where access to the networks is possible, isexpected to increase rapidly. However, whilst fourth generation networkscan support communications at high data rate and low latencies fromdevices such as smart phones and tablet computers, it is expected thatfuture wireless communications networks will need to supportcommunications to and from a much wider range of devices, includingreduced complexity devices, machine type communication (MTC) devices,devices which require little or no mobility, high resolution videodisplays and virtual reality headsets. As such, supporting such a widerange of communications devices can represent a technical challenge fora wireless communications network.

A current technical area of interest to those working in the field ofwireless and mobile communications is known as “The Internet of Things”or IoT for short. The 3GPP has proposed to develop technologies forsupporting narrow band (NB)-IoT using an LTE or 4G wireless accessinterface and wireless infrastructure. Such IoT devices are expected tobe low complexity and inexpensive devices requiring infrequentcommunication of relatively low bandwidth data. It is also expected thatthere will be an extremely large number of IoT devices which would needto be supported in a cell of the wireless communications network.Furthermore such NB-IoT devices are likely to be deployed indoors and/orin remote locations, making radio communications challenging.

SUMMARY OF THE DISCLOSURE

In a first embodiment, the present technique provides a terminal devicefor use with a wireless telecommunications network. The terminal devicecomprises a transceiver configured to receive information indicative ofone or more access classes of terminal devices which are permitted toexchange signals with the wireless telecommunications network, and acontroller configured to update the received information to modify theone or more access classes of terminal devices which are permitted toexchange signals with the mobile telecommunications network, thereceived information being updated by the controller according to apredetermined function of time.

In the first embodiment, the present technique also providesinfrastructure equipment for use with a wireless telecommunicationsnetwork. The infrastructure equipment comprises a controller configuredto generate information indicative of one or more access classes ofterminal devices which are permitted to exchange signals with thewireless telecommunications network and to generate a function of timeaccording to which a terminal device of the wireless telecommunicationsnetwork is configured to update the information to modify the one ormore access classes of terminal devices which are permitted to exchangesignals with the mobile telecommunications network. The infrastructureequipment also comprises a transceiver configured to transmit thegenerated information and function of time to the terminal device.

In a second embodiment, the present technique provides a terminal devicefor use with a wireless telecommunications network. The terminal devicescomprises a transceiver configured to exchange signals with the wirelesstelecommunications network using one of a plurality of predeterminedradio frequency resources, and a controller configured to determine asubset of the plurality of predetermined radio frequency resources onthe basis of a network characteristic indicative of a network preferencefor biasing access to each predetermined radio frequency resource and anoperational characteristic associated with the terminal device, and toselect the one of the plurality of predetermined radio frequencyresources from the determined subset.

In the second embodiment, the present technique also providesinfrastructure equipment for use with a wireless telecommunicationsnetwork. The infrastructure equipment comprises a controller configuredto generate a network characteristic indicative of a network preferencefor biasing access to each of a plurality of predetermined radiofrequency resource by a terminal device of the wirelesstelecommunications network, the network characteristic determined foreach predetermined radio frequency resource being for use by theterminal device in selecting one of the plurality of predetermined radiofrequency resources. The infrastructure equipment also comprises atransceiver configured to transmit, to the terminal device, thegenerated network characteristic indicative of the network preferencefor biasing access to each of the plurality of predetermined radiofrequency resource by the terminal device, and to exchange signals withthe terminal device using the one of a plurality of predetermined radiofrequency resources.

Further respective aspects and features are defined by the appendedclaims.

The foregoing paragraphs have been provided by way of generalintroduction, and are not intended to limit the scope of the followingclaims. The described embodiments, together with further advantages,will be best understood by reference to the following detaileddescription taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the disclosure and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings wherein likereference numerals designate identical or corresponding parts throughoutthe several views, and wherein:

FIG. 1 is a schematic block diagram illustrating an example of a mobiletelecommunication system;

FIG. 2 is a schematic representation illustrating a frame structure of adown-link of a wireless access interface according to an LTE standard;

FIG. 3 is a schematic representation illustrating a frame structure ofan up-link of wireless access interface according to an LTE standard;

FIG. 4 is a schematic block diagram of a terminal device andinfrastructure equipment according to first and second embodiments ofthe present technique;

FIG. 5 schematically illustrates a method according to the firstembodiment of the present technique;

FIG. 6A shows a flow chart schematically illustrating a method ascarried out by a terminal device according to the first embodiment ofthe present technique;

FIG. 6B shows a flow chart schematically illustrating a method ascarried out by infrastructure equipment according to the firstembodiment of the present technique;

FIG. 7 schematically illustrates a method according to the secondembodiment of the present technique;

FIG. 8A shows a flow chart schematically illustrating a method ascarried out by a terminal device according to the second embodiment ofthe present technique; and

FIG. 8B shows a flow chart schematically illustrating a method ascarried out by infrastructure equipment according to the secondembodiment of the present technique.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Conventional Communications System

FIG. 1 provides a schematic diagram illustrating some basicfunctionality of a mobile telecommunications network/system 100operating in accordance with LTE principles and which may be adapted toimplement embodiments of the disclosure as described further below.Various elements of FIG. 1 and their respective modes of operation arewell-known and defined in the relevant standards administered by the3GPP® body, and also described in many books on the subject, forexample, Holma H. and Toskala A [1]. It will be appreciated thatoperational aspects of the telecommunications network which are notspecifically described below may be implemented in accordance with anyknown techniques, for example according to the relevant standards.

The network 100 includes a plurality of base stations 101 connected to acore network 102. Each base station provides a coverage area 103 (i.e. acell) within which data can be communicated to and from communicationsdevices 104. Data is transmitted from base stations 101 tocommunications devices 104 within their respective coverage areas 103via a radio downlink. Data is transmitted from communications devices104 to the base stations 101 via a radio uplink. The uplink and downlinkcommunications are made using radio resources that are licenced forexclusive use by the operator of the network 100. The core network 102routes data to and from the communications devices 104 via therespective base stations 101 and provides functions such asauthentication, mobility management, charging and so on. Communicationsdevices may also be referred to as mobile stations, user equipment (UE),user device, mobile radio, terminal device and so forth. Base stationsmay also be referred to as transceiver stations/NodeBs/eNodeBs (eNB forshort), and so forth. A base station is an example of infrastructureequipment.

Wireless communications systems such as those arranged in accordancewith the 3GPP defined Long Term Evolution (LTE) architecture use anorthogonal frequency'division modulation (OFDM) based interface for theradio downlink (so-called OFDMA) and a single carrier frequency divisionmultiple access scheme (SC-FDMA) on the radio uplink.

FIG. 2 provides a simplified schematic diagram of the structure of adownlink of a wireless access interface that may be provided by or inassociation with the eNB of FIG. 1 when the communications system isoperating in accordance with the LTE standard. In LTE systems thewireless access interface of the downlink from an eNB to a UE is basedupon an orthogonal frequency division multiplexing (OFDM) access radiointerface. In an OFDM interface the resources of the available bandwidthare divided in frequency into a plurality of orthogonal subcarriers anddata is transmitted in parallel on a plurality of orthogonalsubcarriers, where bandwidths between 1.25 MHZ and 20 MHz bandwidth maybe divided into 128 to 2048 orthogonal subcarriers for example. Eachsubcarrier bandwidth may take any value but in LTE it is conventionallyfixed at 15 KHz. However it has been proposed in the future [2][3] toprovide also a reduced subcarrier spacing of 3.75 kHz for certain partsof the LTE wireless access interface for both the uplink and thedownlink. As shown in FIG. 2, the resources of the wireless accessinterface are also temporally divided into frames where a frame 200lasts 10 ms and is subdivided into 10 subframes 201 each with a durationof 1 ms. Each subframe is formed from 14 OFDM symbols and is dividedinto two slots each of which comprise six or seven OFDM symbolsdepending on whether a normal or extended cyclic prefix is beingutilised between OFDM symbols for the reduction of inter symbolinterference. The resources within a slot may be divided into resourcesblocks 203 each comprising 12 subcarriers for the duration of one slotand the resources blocks further divided into resource elements 204which span one subcarrier for one OFDM symbol, where each rectangle 204represents a resource element. More details of the down-link structureof the LTE wireless access interface are provided in Annex 1.

FIG. 3 provides a simplified schematic diagram of the structure of anuplink of an LTE wireless access interface that may be provided by or inassociation with the eNB of FIG. 1. In LTE networks the uplink wirelessaccess interface is based upon a single carrier frequency divisionmultiplexing FDM (SC-FDM) interface and downlink and uplink wirelessaccess interfaces may be provided by frequency division duplexing (FDD)or time division duplexing (TDD), where in TDD implementations subframesswitch between uplink and downlink subframes in accordance withpredefined patterns. However, regardless of the form of duplexing used,a common uplink frame structure is utilised. The simplified structure ofFIG. 3 illustrates such an uplink frame in an FDD implementation. Aframe 300 is divided in to 10 subframes 301 of 1 ms duration where eachsubframe 301 comprises two slots 302 of 0.5 ms duration. Each slot isthen formed from seven OFDM symbols 303 where a cyclic prefix 304 isinserted between each symbol in a manner equivalent to that in downlinksubframes. In FIG. 3 a normal cyclic prefix is used and therefore thereare seven OFDM symbols within a subframe, however, if an extended cyclicprefix were to be used, each slot would contain only six OFDM symbols.The resources of the uplink subframes are also divided into resourceblocks and resource elements in a similar manner to downlink subframes.More details of the LTE up-link represented in FIG. 3 are provided inAnnex 1.

Narrowband Internet of Things

As explained above, it has been proposed to develop an adaptation of amobile communications network (NW) to accommodate narrow bandcommunications within an existing wireless access interface which hasbeen developed to provide broadband wireless communications. Forexample, in 3GPP a project relating to improvements to LTE wirelessaccess interfaces to provide for a Narrowband Internet of Things(NB-IoT) was agreed [2]. This project is aimed at improved indoorcoverage, support for a massive number of low throughput devices, lowdelay sensitivity, ultra-low device cost, low device power consumptionand (optimised) network architecture. An example of such a device is asmart meter. It has been proposed that an NB-IoT communications systemsupports a bandwidth of only 180 kHz and can have three operationalmodes:

-   -   1. ‘Stand-alone operation’ utilizing for example the spectrum        currently being used by GERAN systems as a replacement of one or        more GSM carriers    -   2. ‘Guard band operation’ utilizing the unused resource blocks        within an LTE carrier's guard-band    -   3. ‘In-band operation’ utilizing resource blocks within a normal        LTE carrier

NB-IoT is expected to support a large number of devices (for example,over 50,000) per cell. When there are multiple bands which supportNB-IoT operation (that is, multiple NB-IoT carriers), the network candistribute the UEs among the different NB-IoT bands/carriers.

It is known in wireless telecommunications systems such as LTE and UMTSto have access classes in the range 0-15. Access classes 0-9 areassigned to normal UEs, and have equal priority. These values aredistributed evenly amongst UEs in order that each access class will beassociated with approximately 10% of UEs (so 10% of UEs will have accessclass 0, another 10% of UEs will have access class 1, another 10% of UEswill have access class 2, etc.). Access class 10 is used by UEs whichare establishing an emergency call in order to allow prioritization ofthis call type. Access classes 11-15 each have specific meanings, andare allocated to high priority devices such as those used by publicsafety services.

In LTE, currently a UE using access class (AC) 0-9 will draw a randomnumber in the range 0-1. The UE then compares this random number to abroadcast threshold. If the random number is less than the thresholdthen the UE is allowed to access the cell, otherwise it is barred for atime period indicated by the network, before attempting to access again.This method allows the network to prevent a percentage of UEs fromaccessing in times of high load/congestion. In UMTS, and also forextended access barring (EAB) for MTC devices, the network broadcasts abarring bitmap of 10 bits which indicates which specific access classesare allowed to access the network.

It has also been agreed that access class control of NB-IoT carrierswill also be implemented using a barring bitmap [4]. A problem, however,is that, in order to allow the different UEs with access classes 0-9(equal priority UEs) an equal opportunity to access the network, thenetwork will typically periodically update the barring bitmap broadcastin system information, so that the allowed access classes vary over timeand no UE remains barred indefinitely (if the network always bars thesame access classes then these unfortunate UEs would always be the oneswithout service, which is undesirable). However, updating of systeminformation requires processing and signalling overhead. Using thelegacy system information update procedure, the network must page allUEs and those UEs must perform system information acquisition. Using thesystem information update procedure for EAB, the UEs need to onlyacquire the EAB System Information Block (SIB). However this still comesat a cost of having to perform SIB reception for each update. There hasalso been some discussion about whether paging is necessary for everySIB update for NB-IOT barring. An alternative would be that a UE isrequired to check SIB before accessing each time. However, this meansthat in case there is no barring (usual case), this adds the unnecessaryadditional SIB reception every time the UE needs to access the network.There is therefore a need to provide a way of implementing NB-IoT accessclass control with reduced processing and signalling overhead.

FIG. 4 provides an example block diagram of a terminal device or UE 104and a base station or eNB 101 in accordance with first and secondembodiments of the present technique. As shown in FIG. 4, a UE 104includes a transmitter 401 and a receiver 402 (which together act as atransceiver) which are controlled by a controller 403. Correspondingly,the eNB 101 includes a transmitter 411 and a receiver 412 (whichtogether act as a transceiver) which are controlled by a controller 413which can be referred to as a scheduler. As explained above, the UE 104transmits and receives signals to and from the eNB 101 via a wirelessaccess interface provided by the eNB as part of the wirelesscommunications network.

In the first embodiment of the present technique, a barring bitmaptransmitted to each UE 104 by the cell is updated as a predeterminedfunction of time, so that the access classes which are allowed/notallowed to access a particular NB-IoT carrier vary over time withoutrequiring the barring bitmap to be updated in system information. Theprocessing and signalling overhead associated with each update of thebarring bitmap being included in the system information is thereforealleviated.

In an embodiment, access class barring is enabled/disabled and updatedusing paging from the network. This means that there is no need toperform the SIB acquisition before every access attempt, because each UE104 will be informed via paging and/or value tag update that the barringbitmap has been changed. The UE 104 then applies a time function todetermine the actual barring bitmap to be used based on the receivedbarring bitmap and the system frame number (SFN) or hyper-system framenumber (H-SFN—this is an extension to SFN which has been introduced forextended discontinuous reception (DRX) in LTE and will be applied toNB-IOT). Based on the broadcast and received barring bitmap, and the SFNor H-SFN, the UE 104 knows the time window in which it will be allowedto access. There is therefore no need to check the system informationbefore access, no need to apply an additional barring timer, and no needto frequently update the system information.

It is noted that the present embodiment has a similar effect asproviding a threshold percentage and a barring time, as per the legacyLTE access class barring. However, with the present embodiment, thebarring bitmap can be specifically chosen, so that the network knows andcontrols what specific UEs are barred at any point of time rather thanrelying on a randomly drawn number.

To be clear, a barring bitmap is therefore initially transmitted to theUE 104 by the network via a system information broadcast message or thelike. The barring bitmap is then updated one or more times according toa predetermined function of time known to the UE 104. A new barringbitmap therefore does not have to be transmitted to the UE 104 by thenetwork every time the barring bitmap is to be updated. Rather, thebarring bitmap is updated in accordance with the predetermined functionof time. Eventually, a new barring bitmap may be transmitted to the UE104 by the network so as to provide a new sequence of barring bitmaps tobe used (as determined by the predetermined function of time). In thiscase, the UE 104 is informed of the existence of the new barring bitmapvia paging or the like, and the UE 104 then receives the new barringbitmap again via a system information broadcast message. However, itwill be appreciated that, due to the use of the predetermined functionof time for generating updated barring bitmaps, the need for such newbarring bitmaps to be transmitted to the UE 104 occurs less oftencompared to the case in which a new barring bitmap must be transmittedto the UE 104 by the network every time the barring bitmap is to beupdated. In this description, the original barring bitmap received bythe UE 104 from the network and to which the predetermined function oftime is applied to generate updated barring bitmaps may be referred toas the initial barring bitmap.

The following provides an example of how the present embodiment may beimplemented. In this case, the initial barring bitmap is set to1100000000 (meaning that access classes 0 and 1 from the access classrange 0 to 9 are barred). The UE 104 then updates the barring bitmapeach time H-SFN mod N=0 for successively increasing H-SFN, so that thebitmap is updated every N H-SFNs. An example of the barring bitmapswhich may be generated from the initial barring bitmap using such acalculation is shown in Table 1.

TABLE 1 H-SFN Barring bitmap 0 1100000000 N 0011000000 2N 0000110000 3N0000001100 4N 0000000011 5N 1100000000 6N 0011000000 . . . . . .

It can be seen here that the bit map is shifted by two points to theright after every N hyper-frames. In this example, there are 5 differentbitmaps (the initial barring bitmap plus four possible updates achievedby the bitmap shifting), and thus once H-SFN=5N, the bitmap for H-SFN=0is re-used. In this way, the different possible bitmaps are periodicallycycled through.

In another example, the initial barring bitmap is again set to1100000000 (meaning that access classes 0 and 1 from the access classrange 0 to 9 are barred) and there are again four possible updatesachieved by bitmap shifting. This gives 5 different bitmaps. Each of the5 different bitmaps are then indexed with a respective number from 0 to4, and for a given H-SFN, the UE 104 applies the barring bitmap indexedby

$\left\lfloor \frac{H - {SFN}}{N} \right\rfloor{mod}\mspace{14mu} 5.$More generally, when there are M possible barring bitmaps (including theinitial barring bitmap, plus all possible updates, although since theinitial barring bitmap itself can also be considered as a bitmap update,it can be said that there are M possible bitmap updates), each bitmap isindexed with a respective number from 0 to M−1, and for a given H-SFN,the UE 104 applies the barring bitmap indexed by

$\left\lfloor \frac{H - {SFN}}{N} \right\rfloor{mod}\mspace{14mu}{M.}$Here, the bitmap is again updated every N H-SFNs, and M is the totalnumber of different bitmaps. An example of the barring bitmaps which maybe generated from the initial barring bitmap using such a calculation isshown in Table 2 for M=5.

TABLE 2$\left\lfloor \frac{H - {SFN}}{N} \right\rfloor{mod}\mspace{14mu} M$Barring bitmap 0 1100000000 1 0011000000 2 0000110000 3 0000001100 40000000011

Thus, for example, if N=5, then for H-SFN=0, 1, 2, 3 and 4,

${\left\lfloor \frac{H - {SFN}}{N} \right\rfloor{mod}\mspace{14mu} M} = 0$and thus the bitmap 1100000000 is used. Then, for H-SFN=5, 6,7,8 and 9,

${\left\lfloor \frac{H - {SFN}}{N} \right\rfloor{mod}\mspace{14mu} M} = 1$and thus the bitmap 0011000000 is used.

It will be appreciated that descriptions of Tables 1 and 2 are onlyexamples, and that, in general, the network will be able to control thetime period after which the barring bitmap is to be updated (forexample, every H-SFN, every N H-SFNs, and so on) and to specify how thepattern is to be updated (the time period and updated barring bitmappatterns being defined as part of the predetermined function of time).

For example, instead of shifting the bitmap, another example would be toprovide several explicit patterns, which are activated at certain times.

For example, the network may provide the following bitmaps:

a) 1010100000

b) 0101011111

The network may then control the UE 104 to switch bitmap every 8 H-SFN(for example) by providing a parameter specifying the number of H-SFNs(8, in this case) after which the bitmap should be switched from (a) to(b) and vice versa.

Thus, it will be appreciated that, with embodiments of the presenttechnique, the need for frequent updates to system information to changebarred access classes (in particular, barred access classes for NB-IoTcarriers) and to thus allow fair network access to all UEs isalleviated. This reduces the processing and signalling overheadassociated with such updates. The UE power consumption associated withfrequent reading of system information, either upon SIB update, orbefore every access, is also reduced. The arrangement is also moredeterministic (compared to, for example, determining whether a UE is tobe granted access based on the generation of a random number).

It is noted that the predetermined function of time may be transmittedto the UE in the system information broadcast message or the like alongwith the barring bitmap. In this case, each time a new barring bitmap istransmitted to the UE, a new predetermined function of time may also betransmitted to the UE for use with the new barring bitmap.Alternatively, the same predetermined function of time may be used (andmay or may not be re-transmitted with the new barring bitmap).Alternatively the predetermined function of time can be signaled to UEsvia unicast signaling, or groupwise signalling, allowing different UEsto attach to the network with different latencies.

It will be appreciated that although, in the above-mentionedembodiments, the barred and non-barred access classes are represented bya bitmap, this is just an example, and any other information indicativeof one or more access classes of terminal devices which are permitted toexchange signals with the wireless telecommunications network may beused. Thus, more generally, it is the information (of which the bitmapis an example) which is updated in the way that has been described.

It will thus be appreciated that the first embodiment of the presenttechnique provides, in general, a terminal device (for example, terminaldevice 104) for use with a wireless telecommunications network.

The terminal device comprises a transceiver (implemented, for example,using transmitter 401 and receiver 402) configured to receiveinformation indicative of one or more access classes of terminal deviceswhich are permitted to exchange signals with the wirelesstelecommunications network. The terminal device also comprises acontroller (for example, controller 403) configured to update thereceived information to modify the one or more access classes ofterminal devices which are permitted to exchange signals with the mobiletelecommunications network, the received information being updated bythe controller according to a predetermined function of time.

In an embodiment, the controller is configured to control thetransceiver to exchange signals with the wireless telecommunicationsnetwork at a particular time when an access class of the terminal devicematches one of the one or more access classes of terminal devices whichare permitted to exchange signals with the wireless telecommunicationsnetwork at that particular time.

In an embodiment, the transceiver is configured to receive at least oneof the information and the predetermined function of time via a systeminformation broadcast message from the wireless telecommunicationsnetwork.

In an embodiment, the information indicative of the one or more accessclasses of terminal devices which are permitted to exchange signals withthe wireless telecommunications network is a bitmap, wherein theposition of each bit in the bitmap is indicative of a respective accessclass and the bit at each position is indicative of whether or not thataccess class is permitted to exchange signals with the wirelesstelecommunications network.

In an embodiment, the controller is operable to periodically update thereceived information at a time period and in a manner specified by thepredetermined function of time. When the information is a bitmap, eachupdate of the bitmap may comprise performing a shift operation onelements of the bitmap in accordance with a predetermined rule (asdescribed with reference to Tables 1 and 2, for example). Alternatively,each update of the bitmap may comprise defining the bitmap as one of aplurality of predetermined bitmaps. In an embodiment, the possibleupdates of the information are consecutively applied and periodicallyrepeated. In other words, the possible updates of the informationaccording to the predetermined function of time are cycled through andthe cycle is then repeated (this would result in, for example, thebitmap being sequentially updated to each of the barring bitmaps shownin Tables 1 and 2—once the final bitmap corresponding to H-SFN=4N or theindex

${\left\lfloor \frac{H - {SFN}}{N} \right\rfloor{mod}\mspace{14mu} M} = {M - 1}$has been used, the sequence returns to the first bitmap corresponding toH-SFN=0 or the index

${{\left\lfloor \frac{H - {SFN}}{N} \right\rfloor{mod}\mspace{14mu} M} = 0},$and the sequence is repeated).

In an embodiment, the time period at which the received information isperiodically updated is defined with reference to a time changingparameter associated with successive radio frames via which thetransceiver is configured to exchange signals with the wirelesstelecommunications network. For example, the time changing parameter isa system frame number (SFN) or Hyper-system frame number (H-SFN) ofsuccessive radio frames In one example, the time period at which thereceived information is periodically updated is defined by apredetermined number N of SFNs or H-SFNs.

For example, the update to the information is applied when the followingequation is satisfied:H-SFN Mod N=0

Such an example is described with reference to Table 1.

In another example, there are M possible updates to the informationindicative of the one or more access classes of terminal devices whichare permitted to exchange signals with the wireless telecommunicationsnetwork. Each possible update is associated with a respective indexvalue from 0 to M−1, and the update of the information used to definethe one or more access classes of terminal devices which are permittedto exchange signals with the wireless telecommunications network for agiven H-SFN is the update with index:

$\left\lfloor \frac{H - {SFN}}{N} \right\rfloor{mod}\mspace{14mu} M$

Such an example is described with reference to Table 2.

In an embodiment, the terminal device is a Narrowband Internet of Things(NB-IoT) terminal device.

It will also be appreciated that the first embodiment of the presenttechnique provides, in general, infrastructure equipment (such as basestation 101) for use with the wireless telecommunications network. Theinfrastructure equipment comprises a controller (such as controller 413)configured to generate the information indicative of one or more accessclasses of terminal devices which are permitted to exchange signals withthe wireless telecommunications network and to generate a function oftime according to which the terminal device (such as terminal device104) is configured to update the information to modify the one or moreaccess classes of terminal devices which are permitted to exchangesignals with the mobile telecommunications network. The infrastructurealso comprises a transceiver (implemented using transmitter 411 andreceiver 412, for example) configured to transmit the generatedinformation and the function of time to the terminal device. In thiscase, the function of time generated by the controller and transmittedto the terminal device is the predetermined function of time.

FIGS. 5 and 6A-B schematically illustrate a method according to thefirst embodiment.

In FIG. 5, it is seen that, at step 501, the infrastructure equipment(in the form of eNB 101) generates the information indicative of the oneor more access classes of terminal devices which are permitted toexchange signals with the wireless telecommunications network andgenerates the function of time according to which the terminal device104 is configured to update the information to modify the one or moreaccess classes of terminal devices which are permitted to exchangesignals with the mobile telecommunications network. The generatedinformation and function of time are then transmitted to the terminaldevice 104. Then, at step 502, once the generated information andfunction of time are received by the terminal device 104, the terminaldevice 104 updates the received information to modify the one or moreaccess classes of terminal devices which are permitted to exchangesignals with the mobile telecommunications network, the receivedinformation being updated by the controller according to the function oftime.

FIG. 6A shows a flow chart schematically illustrating the method carriedout by the controller 403 of the terminal device 104. The method startsat step 601. At step 602, the controller 403 controls the transceiver401, 402 of the terminal device to receive the information (which, inthis case, is a barring bitmap) indicative of the one or more accessclasses of terminal devices which are permitted to exchange signals withthe wireless telecommunications network. At step 603, the controller 403updates the received information to modify the one or more accessclasses of terminal devices which are permitted to exchange signals withthe mobile telecommunications network, the received information beingupdated by the controller according to the predetermined function oftime. In one embodiment, the predetermined function of time is thefunction of time generated by the infrastructure equipment andtransmitted to the terminal device 104 with the initial information. Themethod ends at step 604.

FIG. 6B shows a flow chart schematically illustrating the method carriedout by the controller 413 of the infrastructure equipment (in the formof eNB 101). The method starts at step 605. At step 606, the controller413 generates the information indicative of the one or more accessclasses of terminal devices which are permitted to exchange signals withthe wireless telecommunications network. At step 607, the controller 413generates the function of time according to which the terminal device104 is configured to update the information to modify the one or moreaccess classes of terminal devices which are permitted to exchangesignals with the mobile telecommunications network. At step 608, thecontroller 413 controls the transceiver 411, 412 of the infrastructureequipment to transmit the generated information and function of time tothe terminal device. The method ends at step 609.

It is noted that in an alternative embodiment, the infrastructureequipment may transmit only the initial information to the terminaldevice, and the predetermined function of time may be known to thecontroller 403 of the terminal device in advance. In this case, afunction of time does not need to be generated by the infrastructureequipment and transmitted to the terminal device with the initialinformation, since the predetermined function of time is already knownto the controller 403. It is also noted that Multiple NB-IoT carriers(each 180 kHz) can be configured within a system bandwidth. For example,Multiple NB-IoT carriers each occupying a single physical resource block(PRB) can be configured in-band within an LTE system. It has beenproposed that for a Multiple NB-IoT carrier operation, a primary carrier(also referred to as an anchor carrier) and multiple secondary carriersare used, wherein a primary carrier contains synchronisation channelssuch as narrow band primary synchronisation signals (NB-PSS)/narrow bandsecondary synchronisation signals (NB-SSS) and common control channelssuch as Master Information Block (MIB, carried by narrow band physicalbroadcast channel (NB-PBCH)) and SIBs. The primary carriers can containunicast traffic in addition. The secondary carriers contain unicasttraffic, but do not contain the full set of synchronisation and controlchannels. This arrangement reduces the control channel overheads byavoiding having synchronisation & common control channels in everyNB-IoT carrier. Multiple NB-IoT carriers can also be deployed when thereis a mixture of guard-band and in-band NB-IoT carriers. For example, theguard-band NB-IoT carrier can be the primary carrier whilst the in-bandNB-IoT carriers are secondary carriers.

As previously mentioned, NB-IoT is expected to support a large number ofdevices (for example, over 50,000) per cell. For a Multiple NB-IoTcarriers operation, the network can distribute the UEs among thedifferent secondary carriers.

In order to access the network, the NB-IoT device performs a RandomAccess procedure. For a Multiple NB-IoT carriers operation, some of thesecondary carriers (and possibly the primary carrier) can be configuredwith Physical Random Access Channel (PRACH) resources and these areindicated in the SIB. Typically, a UE would select the PRACH resourcebased on criteria (for example, its coverage level, as in enhanced MTC(eMTC)) and for those PRACH resources corresponding to the criteria, theUE would randomly select one. The selected PRACH resource may belong toa secondary band experiencing high load and may not be able to serve theNB-IoT device. If multiple secondary bands are congested then suchattempts may waste UE battery power and cause congestion in theresources (for example, PRACH resources) of that band. There istherefore a need to provide a way for an NB-IoT device to select anappropriate NB-IoT band for Random Access which alleviates theseproblems.

Thus, according to the second embodiment of the present technique,individual restrictions are imposed on each of the NB-IoT bands under aMultiple NB-IoT carriers operation. The parameters forming thisrestriction are indicated in the SIB.

In one embodiment, the Access Class Barring (ACB) mechanism (aspreviously mentioned) is extended for each NB-IoT band that isconfigured with RACH resources (in particular, PRACH resources) under aMultiple NB-IoT carriers operation. The ACB configurations for eachNB-IoT band (secondary bands or primary band) are indicated in the SIB(which may reside in the primary band) and provide further band specificparameters which the UE 104 needs to use in addition to the barringbitmap to calculate whether access is allowed.

For example, consider a Multiple NB-IoT carriers operation with 3secondary bands (Secondary Band #1, Secondary Band #2 and Secondary Band#3) and a primary band. The ACB can be configured as shown in Table 3.Here the Primary Band and Secondary Band #2 are heavily loaded and soonly allow a single Access Class (AC) (AC0 and AC6, respectively) toaccess the NB-IoT band. Secondary Band #3 is not congested and can allowall UEs to access it.

TABLE 3 NB-IoT Access Class Bands 0 1 2 3 4 5 6 7 8 9 Primary ✓ x x x xx x x x x Secondary x ✓ ✓ ✓ x x x x x x #1 Secondary x x x x x x ✓ x x x#2 Secondary ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓ #3

In one embodiment, for those NB-IoT bands in which the UE 104 is notbarred, it may select the NB-IoT band with the highest measured signalstrength or quality. One such measurement is the reference signalreceived power (RSRP).

In another embodiment, for those NB-IoT bands in which the UE 104 is notbarred, the UE would select a band randomly (based on a uniformdistribution, for example).

In another embodiment, for those NB-IoT bands in which the UE 104 is notbarred, it would select the NB-IoT band with the least number of barredAccess Class (AC). This aspect recognises that the number of barred ACis an indication that a band is congested. For example in Table 3, a UEwith AC=2 is able to access Secondary Band #1 and Secondary Band #3.Since Secondary Band #3 has more Access Classes not barred, the UE willfirstly attempt to access Secondary Band #3. If it fails to access itafter a predefined number of attempts, it will try to access the bandwith the second least barred AC. For cases where two or more bands haveequal number of ACs being barred, the UE may select one of them randomlybased on uniform distribution, for example.

In another embodiment, a restriction to allow a subset of UEs (that arenot barred) to access the network at a time is applied. This restrictionis based on an identifier of each UE (UE_ID, such as its TemporaryMobile Subscriber Identity (TMSI)) and a MOD function. For example, a UEwith UE_ID can access a non-barred band (sub-band) if the following istrue:sub-band=UE_ID MOD n

Here, n is the number of sub-bands and each sub-band is allocated aninteger value from 0 to n−1 (meaning that each UE_ID will yield a valueof UE_ID MOD n which associates it with one of the sub-bands). The aboveformula will spread UEs of a particular access class evenly amongst theallowed bands, while the barring bitmap is used to control the overallpercentage of UEs on each band (in the example of Table 3, more accessclasses are allowed to access secondary band #3 than other bands, forexample).

In another embodiment, the network signals predetermined values ‘M’,offset values {k₁, k₂, . . . k_(n)} and a constant value ‘C’ to the UEs.The offsets may be specific to each NB-IoT band. The offsets may besignalled as an explicit list (for example, {1,3,5,7}) or may besignalled more compactly as a formula. For example, the formulak_(i)=a*i +b may be used, in which ‘i’ iterates among the offsets and‘a’ and ‘b’ are signalled parameters. Some of the parameters may befixed, or may be a function of the access class, for example. The UEthen determines whether it is eligible to attach to a sub-band that isnot barred (by access class barring) by determining whether thefollowing equation is satisfied for any value of the offset k_(i):(UE_ID+k _(i))mod M=C

The UE then randomly chooses one of the bands for which it is eligible.

Note that the network can cause more UEs to select a certain band byincreasing the number of assigned offsets for that band (assigning morevalues of k_(i) to that band), or by reducing the ‘M’ parameter for thatband. Hence, this embodiment allows congestion on bands to becontrolled.

In another embodiment, the network signals values of ‘M’ and ‘C’ to UEs.The values of ‘M’ and/or ‘C’ may be specific to each band. The UEdetermines whether it is eligible to attach to a sub-band that is notbarred (by access class barring) by determining whether the followingequation is satisfied:UE_ID mod M<C

As per the previously described embodiment, the UE then randomly choosesone of the bands for which it is eligible.

In the above-mentioned embodiments, it is noted that each of the valuesM, C and k_(i) may be integer values.

In another embodiment of the invention, an RSRP offset factor issignalled for each of the NB-IoT carriers. In this case, when selectingan NB-IoT carrier, the UE 104 will perform RSRP measurements on thosecarriers and add the appropriate RSRP offset factor for each NB-IoTcarrier, to create a modified RSRP measurement. The UE may then selectbased on a criterion, such as the NB-IoT carrier with the best RSRP ormodified RSRP measurement, or any of the NB-IoT carriers for which themodified RSRP measurement exceeds a threshold, for example.

Using this embodiment, the network may restrict the number of UEs thatselect different NB-IoT carriers. For a congested carrier, if the RSRPoffset factor is large, only a few UEs will achieve the modified RSRPcriterion (hence restricting the number of UEs that can access thatNB-IoT carrier). In addition, those UEs that do select that congestedcarrier will operate in better channel conditions, will require lessresource for operation and hence will ease the congestion on thatcongested carrier.

As an example of this embodiment, the RSRP factors for different NB-IoTcarriers are shown in Table 4.

TABLE 4 NB-IoT carrier RSRP offset factor Loading Primary −5 dB HighSecondary #1 −2 dB Medium Secondary #2 −5 dB High Secondary #3  +1 dBLow

In this example, the UE may measure the RSRP values and determinemodified RSRP values as shown in Table 5 for the different NB-IoTcarriers, leading to selection of secondary carrier #3.

TABLE 5 RSRP NB-IoT carrier Measured RSRP offset factor Modified RSRPPrimary −95 dBm −5 dB −100 dBm  Secondary #1 −96 dBm −2 dB −98 dBmSecondary #2 −94 dBm −5 dB −99 dBm Secondary #3 −98 dBm  +1 dB −97 dBm

Note that the primary NB-IoT carrier may be power-boosted. The RSRPoffset factor described above can be used to account for the powerboosting factor. For example, if the primary NB-IoT carrier ispower-boosted by 6 dB and the system does not want the UE to select anNB-IoT carrier based on this power-boosting, the RSRP offset factor forthe primary NB-IoT carrier for the system shown in Table 5 could be setas −5 dB−6dB=−11 dB. Alternatively, the modified RSRP value could becalculated as “(measured RSRP)+(RSRP offset factor)−(power boostingfactor)”.

It will be appreciated that instead of the RSRP being used, any othersuitable measure of signal quality may be used (for example the LTEmeasurement known as Reference Signal Received Quality, RSRQ). Thus, theRSRP offset factor (or value) may be, more generally, a signal qualityoffset factor, the RSRP measurement may be, more generally, a signalquality measurement, and the modified RSRP measurement may be, moregenerally, a modified signal quality measurement.

In another embodiment, an Access Class Factor (for example, aprobability taking a value from 0 to 1) is signalled for each NB-IoTband. The UE 104 generates a random number between 0 and 1. The bandswith AC Factor greater than this generated number are candidate NB-IoTbands. The UE selects the band with the AC Factor closest to thisgenerated number. For example, the AC Factor for each band is as listedin Table 6. If the UE generated random number is 0.4, then the candidatebands are Secondary Band #1 (AC Factor=0.5) and Secondary Band #3 (ACFactor=0.9). Since Secondary Band #1 has an AC Factor closer to thisgenerated number, the UE will select Secondary Band #1. The network canthen set a high AC Factor for bands that are less congested andvice-versa for bands that more congested. It will also be appreciatedthat an alternative arrangement could be implemented in which thenetwork sets a high AC Factor for bands that are more congested andvice-versa for bands that are less congested. In this case, it will bethe bands with a lower AC Factor than the number randomly generated bythe UE which are determined as the candidate bands.

TABLE 6 NB-IoT Bands AC Factor Primary Band 0.1 Secondary Band #1 0.5Secondary Band #2 0.1 Secondary Band #3 0.9

In another embodiment, among the bands that have AC Factors greater than(or, in the alternative arrangement, less than) the UE generated randomnumber, the UE selects the band with the highest measured signalstrength or quality (for example, RSRP).

In another embodiment, among the NB-IoT bands with AC Factor greaterthan (or, in the alternative arrangement, less than) the UE generatedrandom number, the UE randomly selects one of these NB-IoT bands (wing auniform distribution, for example).

It should be appreciated that selection criteria can be a combination oftwo or more of the above embodiments. For example, an ACB can be used asa first congestion control followed by signal quality offset. In thiscase, the UE only allocates the signal quality offset values andcalculates a modified signal quality measurement for NB-IoT bands thatare not barred by the ACB.

It will thus be appreciated that the second embodiment of the presenttechnique provides, in general, a terminal device (such as terminaldevice 104) for use with a wireless telecommunications network. Theterminal device comprises a transceiver (implemented using, for example,transmitter 401 and receiver 402) configured to exchange signals withthe wireless telecommunications network using one of a plurality ofpredetermined radio frequency resources. The terminal device alsocomprises a controller (such as controller 403) configured to determinea subset of the plurality of predetermined radio frequency resources onthe basis of a network characteristic indicative of a network preferencefor biasing access to each predetermined radio frequency resource and anoperational characteristic associated with the terminal device, and toselect the one of the plurality of predetermined radio frequencyresources from the determined subset.

In an embodiment, each of the plurality of predetermined radio frequencyresources is a Narrowband Internet of Things (NB-IoT) carrier.

In an embodiment, the network characteristic indicative of the networkpreference for biasing access to each predetermined radio frequencyresource is a number of access classes of terminal devices which arepermitted to exchange signals with the wireless telecommunicationsnetwork using that predetermined radio frequency resource and theoperational characteristic associated with the terminal device is anaccess class of the terminal device. The controller is configured toinclude each predetermined radio frequency resource via which terminaldevices with the access class of the terminal device are permitted toexchange signals with the wireless telecommunications network in thesubset of the plurality of predetermined radio frequency resources. Anexample of this embodiment is described with reference to Table 3.

In an embodiment, the controller is configured to select, from thepredetermined radio frequency resources of the subset, the predeterminedradio frequency resource associated with the largest number of accessclasses of terminal devices which are permitted to exchange signals withthe wireless telecommunications network using that predetermined radiofrequency resource as the one of the plurality of predetermined radiofrequency resources.

In an embodiment, the network characteristic indicative of the networkpreference for biasing access to each predetermined radio frequencyresource is a signal quality offset value associated with thatpredetermined radio frequency resource and the operationalcharacteristic associated with the terminal device is a signal qualitymeasurement associated with each predetermined radio frequency resource.An example of this embodiment is described with reference to Tables 3and 4.

In one embodiment, the controller is configured to include, in thesubset of the plurality of predetermined radio frequency resources, eachpredetermined radio frequency resource associated with a modified signalquality measurement which exceeds a predetermined threshold, themodified signal quality measurement associated with each predeterminedradio frequency resource being given by the signal quality measurementassociated with that predetermined frequency resource added to thesignal quality offset value associated with that predetermined radiofrequency resource. In another embodiment, the controller is configuredto include, in the subset of the plurality of predetermined radiofrequency resources, a predetermined radio frequency resource associatedwith a highest modified signal quality measurement, the modified signalquality measurement associated with each predetermined radio frequencyresource being given by the signal quality measurement associated withthat predetermined frequency resource added to the signal quality offsetvalue associated with that predetermined radio frequency resource.

In an embodiment, the calculation of the signal quality offset valueassociated with each predetermined radio frequency resource takes intoaccount the effect of a signal quality boosting value associated withthat predetermined radio frequency resource.

In an embodiment, for each predetermined radio frequency resource, thesignal quality measurement is a Reference Signal Received Power (RSRP)measurement, the signal quality offset value is an RSRP offset value andthe modified signal quality measurement is a modified RSRP measurement,wherein the RSRP offset value serves to reduce the modified RSRPmeasurement relative to the RSRP measurement for a predetermined radiofrequency resource with a lower level of network preference for biasingaccess to that predetermined radio frequency resource and to increasethe modified RSRP measurement relative to the RSRP measurement for apredetermined radio frequency resource with a higher level of networkpreference for biasing access to that predetermined radio frequencyresource.

In an embodiment, the network characteristic indicative of the networkpreference for biasing access to each predetermined radio frequencyresource is an access class factor associated with that predeterminedradio frequency resource, the access class factor being a value within apredetermined range and being correlated with the level of networkpreference for biasing access to that predetermined radio frequencyresource, and the operational characteristic associated with theterminal device is a randomly generated value within the predeterminedrange. The controller is configured to include, in the subset of theplurality of predetermined radio frequency resources, each predeterminedradio frequency resource which either, in the case that the access classfactor of each predetermined radio frequency resource is positivelycorrelated with the level of network preference for biasing access tothat radio frequency resource, has an access class factor greater thanthe randomly generated value of the terminal device, or, in the casethat the access class factor of each predetermined radio frequencyresource is negatively correlated with the level of network preferencefor biasing access to that radio frequency resource, has an access classfactor less than the randomly generated value of the terminal device. Anexample of this embodiment is described with reference to Table 6 (inthis case, the access class factor associated with each predeterminedradio frequency resource is positively correlated with the level ofnetwork preference for biasing access to that predetermined radioresource).

In an embodiment, the predetermined range is from 0 to 1, and the accessclass factor is positively correlated with the level of the networkpreference for biasing access to each predetermined radio frequencyresource (again, this is the case with the example of Table 6).

In an embodiment, the controller is configured to select, from thepredetermined radio frequency resources of the subset, the predeterminedradio frequency resource associated with the access class factor whichis closest to the randomly generated value of the terminal device.

It will furthermore be appreciated that for each of the above-mentionedembodiments, when the one of the plurality of predetermined radiofrequency resources is not chosen in a way specific to the method used,the controller may select, from the predetermined radio frequencyresources of the subset, the predetermined radio frequency resourceassociated with the highest signal strength or signal quality as the oneof the plurality of predetermined radio frequency resources.

Alternatively, the controller may be configured to randomly select, fromthe predetermined radio frequency resources of the subset, the one ofthe plurality of predetermined radio frequency resources.

Alternatively, the controller may be configured to select, from thepredetermined radio frequency resources of the subset, the one of theplurality of predetermined radio frequency resources based on anidentifier, UE_ID, of the terminal device.

For example, in one embodiment, there are n predetermined radiofrequency resources in the subset and each predetermined radio frequencyresource in the subset is associated with one of a respective integeridentifier from 0 to n−1, and the controller is configured to select asthe one of the plurality predetermined radio frequency resources thepredetermined radio frequency resource with an identifier which is equalto UE-ID mod n.

In another embodiment, each predetermined radio frequency resource inthe subset is associated with a respective one or more of predeterminedoffset values k_(i), and the controller is configured to select as theone of the plurality of predetermined radio frequency resources apredetermined radio frequency resource associated with an offset valuek_(i) which satisfies:(UE_ID+k _(i))mod M=C

wherein M and C are predetermined values. In one embodiment, C isconstant for each predetermined radio frequency resource in the subsetwhereas M may be different for each predetermined radio frequencyresource in the subset.

In another embodiment, each predetermined radio frequency resource inthe subset is associated with a respective predetermined value M and arespective predetermined value C, and the controller is configured toselect as the one of the plurality of predetermined radio frequencyresources a predetermined radio frequency resource with respectivepredetermined values M and C which satisfy:UE_ID mod M<C

It will also be appreciated that the second embodiment of the presenttechnique provides, in general, infrastructure equipment (such as basestation 101) for use with the wireless telecommunications network. Theinfrastructure equipment comprises a controller (such as controller 413)configured to generate the network characteristic indicative of thenetwork preference for biasing access to each of the plurality ofpredetermined radio frequency resource by the terminal device (such asterminal device 104), the network characteristic determined for eachpredetermined radio frequency resource being for use by the terminaldevice in selecting the one of the plurality of predetermined radiofrequency resources. The infrastructure equipment also comprises atransceiver (implemented using transmitter 411 and receiver 412, forexample) configured to transmit, to the terminal device, the generatednetwork characteristic indicative of the network preference for biasingaccess to each of the plurality of predetermined radio frequencyresource by the terminal device, and to exchange signals with theterminal device using the one of the plurality of predetermined radiofrequency resources.

FIGS. 7 and 8A-B schematically illustrate a method according to thesecond embodiment.

In FIG. 7, it can be seen that, at step 701, the infrastructureequipment (in the form of eNB 101) generates a network characteristicindicative of a network preference for biasing access to each of aplurality of predetermined radio frequency resource by the terminaldevice 104 of the wireless telecommunications network, the networkcharacteristic determined for each predetermined radio frequencyresource being for use by the terminal device 104 in selecting one ofthe plurality of predetermined radio frequency resources. Theinfrastructure equipment then transmits, to the terminal device 104, thegenerated network characteristic indicative of the network preferencefor biasing access to each of the plurality of predetermined radiofrequency resource by the terminal device 104. At step 702, the terminaldevice 104 determines a subset of the plurality of predetermined radiofrequency resources on the basis of the network characteristicindicative of the network preference for biasing access to eachpredetermined radio frequency resource and an operational characteristicassociated with the terminal device 104. At step 703, the terminaldevice 104 selects the one of the plurality of predetermined radiofrequency resources from the determined subset. At step 704, theterminal device 104 and infrastructure equipment exchange signals usingthe selected one of the plurality of predetermined radio frequencyresources.

FIG. 8A shows a flow chart schematically illustrating the method carriedout by the controller 403 of the terminal device 104. The method startsat step 8A. At step 802, the controller 403 determines the subset of theplurality of predetermined radio frequency resources on the basis of thenetwork characteristic indicative of the network preference for biasingaccess to each predetermined radio frequency resource and theoperational characteristic associated with the terminal device 104. Atstep 803, the controller 403 selects the one of the plurality ofpredetermined radio frequency resources from the determined subset. Atstep 804, the controller 403 controls the transceiver 401, 402 of theterminal device 104 to exchange signals with the wirelesstelecommunications network (for example, via the infrastructureequipment) using the selected one of the plurality of predeterminedradio frequency resources. The method ends at step 805.

FIG. 8B shows a flow chart schematically illustrating the method carriedout by the controller 413 of the infrastructure equipment (in the formof eNB 101). The method starts at step 806. At step 807, the controller413 generates the network characteristic indicative of the networkpreference for biasing access to each of the plurality of predeterminedradio frequency resources by the terminal device 104, the networkcharacteristic determined for each predetermined radio frequencyresource being for use by the terminal device 104 in selecting the oneof the plurality of predetermined radio frequency resources. At step808, the controller 413 controls the transceiver 411, 412 to transmit,to the terminal device 104, the generated network characteristicindicative of the network preference for biasing access to each of theplurality of predetermined radio frequency resource by the terminaldevice 104. At step 809, the controller 413 controls the transceiver411, 412 to exchange signals with the terminal device 104 using the oneof the plurality of predetermined radio frequency resources. The methodends at step 810.

Various embodiments of the present technique are described by thefollowing numbered clauses:

Clause 1. A terminal device for use with a wireless telecommunicationsnetwork, the terminal device comprising:

-   -   a transceiver configured to exchange signals with the wireless        telecommunications network using one of a plurality of        predetermined radio frequency resources; and    -   a controller configured to determine a subset of the plurality        of predetermined radio frequency resources on the basis of a        network characteristic indicative of a network preference for        biasing access to each predetermined radio frequency resource        and an operational characteristic associated with the terminal        device, and to select the one of the plurality of predetermined        radio frequency resources from the determined subset.

Clause 2. A terminal device according to clause 1, wherein each of theplurality of predetermined radio frequency resources is a NarrowbandInternet of Things (NB-IoT) carrier.

Clause 3. A terminal device according to clause 1 or 2, wherein:

-   -   the network characteristic indicative of the network preference        for biasing access to each predetermined radio frequency        resource is a number of access classes of terminal devices which        are permitted to exchange signals with the wireless        telecommunications network using that predetermined radio        frequency resource;    -   the operational characteristic associated with the terminal        device is an access class of the terminal device; and    -   the controller is configured to include each predetermined radio        frequency resource via which terminal devices with the access        class of the terminal device are permitted to exchange signals        with the wireless telecommunications network in the subset of        the plurality of predetermined radio frequency resources.

Clause 4. A terminal device according to clause 3, wherein thecontroller is configured to select, from the predetermined radiofrequency resources of the subset, the predetermined radio frequencyresource associated with the largest number of access classes ofterminal devices which are permitted to exchange signals with thewireless telecommunications network using that predetermined radiofrequency resource as the one of the plurality of predetermined radiofrequency resources.

Clause 5. A terminal device according to clause 1 or 2, wherein:

-   -   the network characteristic indicative of the network preference        for biasing access to each predetermined radio frequency        resource is a signal quality offset value associated with that        predetermined radio frequency resource;    -   the operational characteristic associated with the terminal        device is a signal quality measurement associated with each        predetermined radio frequency resource; and    -   the controller is configured to include, in the subset of the        plurality of predetermined radio frequency resources, each        predetermined radio frequency resource associated with a        modified signal quality measurement which exceeds a        predetermined threshold, the modified signal quality measurement        associated with each predetermined radio frequency resource        being given by the signal quality measurement associated with        that predetermined frequency resource added to the signal        quality offset value associated with that predetermined radio        frequency resource.

Clause 6. A terminal device according to clause 1 or 2, wherein:

-   -   the network characteristic indicative of the network preference        for biasing access to each predetermined radio frequency        resource is a signal quality offset value associated with that        predetermined radio frequency resource;    -   the operational characteristic associated with the terminal        device is a signal quality measurement associated with each        predetermined radio frequency resource; and    -   the controller is configured to include, in the subset of the        plurality of predetermined radio frequency resources, a        predetermined radio frequency resource associated with a highest        modified signal quality measurement, the modified signal quality        measurement associated with each predetermined radio frequency        resource being given by the signal quality measurement        associated with that predetermined frequency resource added to        the signal quality offset value associated with that        predetermined radio frequency resource.

Clause 7. A terminal device according to clause 5 or 6, wherein thecalculation of the signal quality offset value associated with eachpredetermined radio frequency resource takes into account the effect ofa signal quality boosting value associated with that predetermined radiofrequency resource.

Clause 8. A terminal device according to any one of clauses 5 to 7,wherein, for each predetermined radio frequency resource, the signalquality measurement is a Reference Signal Received Power (RSRP)measurement, the signal quality offset value is an RSRP offset value andthe modified signal quality measurement is a modified RSRP measurement,wherein the RSRP offset value serves to reduce the modified RSRPmeasurement relative to the RSRP measurement for a predetermined radiofrequency resource with a lower level of network preference for biasingaccess to that predetermined radio frequency resource and to increasethe modified RSRP measurement relative to the RSRP measurement for apredetermined radio frequency resource with a higher level of networkpreference for biasing access to that predetermined radio frequencyresource.

Clause 9. A terminal device according clause 1 or 2, wherein:

-   -   the network characteristic indicative of the network preference        for biasing access to each predetermined radio frequency        resource is an access class factor associated with that        predetermined radio frequency resource, the access class factor        being a value within a predetermined range and being correlated        with the level of network preference for biasing access to that        predetermined radio frequency resource;    -   the operational characteristic associated with the terminal        device is a randomly generated value within the predetermined        range; and    -   the controller is configured to include, in the subset of the        plurality of predetermined radio frequency resources, each        predetermined radio frequency resource which either:    -   in the case that the access class factor of each predetermined        radio frequency resource is positively correlated with the level        of network preference for biasing access to that radio frequency        resource, has an access class factor greater than the randomly        generated value of the terminal device; or    -   in the case that the access class factor of each predetermined        radio frequency resource is negatively correlated with the level        of network preference for biasing access to that radio frequency        resource, has an access class factor less than the randomly        generated value of the terminal device.

Clause 10. A terminal device according to clause 9, wherein thepredetermined range is from 0 to 1, and the access class factor ispositively correlated with the level of the network preference forbiasing access to each predetermined radio frequency resource.

Clause 11. A terminal device according to clause 9 or 10, wherein thecontroller is configured to select, from the predetermined radiofrequency resources of the subset, the predetermined radio frequencyresource associated with the access class factor which is closest to,the randomly generated value of the terminal device.

Clause 12. A terminal device according to any one of clauses 1 to 3, 5,9 and 10, wherein the controller is configured to select, from thepredetermined radio frequency resources of the subset, the predeterminedradio frequency resource associated with the highest signal strength orsignal quality as the one of the plurality of predetermined radiofrequency resources.

Clause 13. A terminal device according to any one of clauses 1 to 3, 5,9 and 10, wherein the controller is configured to randomly select, fromthe predetermined radio frequency resources of the subset, the one ofthe plurality of predetermined radio frequency resources.

Clause 14. A terminal device according to any one of clauses 1 to 3, 5,9 and 10wherein the controller is configured to select, from thepredetermined radio frequency resources of the subset, the one of theplurality of predetermined radio frequency resources based on anidentifier, UE_ID, of the terminal device.

Clause 15. A terminal device according to clause 14, wherein there are npredetermined radio frequency resources in the subset and eachpredetermined radio frequency resource in the subset is associated withone of a respective integer identifier from 0 to n−1, and the controlleris configured to select as the one of the plurality predetermined radiofrequency resources the predetermined radio frequency resource with anidentifier which is equal to UE-ID mod n.

Clause 16. A terminal device according to clause 14, wherein eachpredetermined radio frequency resource in the subset is associated witha respective one or more of predetermined offset values k_(i), and thecontroller is configured to select as the one of the plurality ofpredetermined radio frequency resources a predetermined radio frequencyresource associated with an offset value k_(i) which satisfies:(UE_ID+ki)mod M=C

wherein M and C are predetermined values.

Clause 17. A terminal device according to clause 14, wherein eachpredetermined radio frequency resource in the subset is associated witha respective predetermined value M and a respective predetermined valueC, and the controller is configured to select as the one of theplurality of predetermined radio frequency resources a predeterminedradio frequency resource with respective predetermined values M and Cwhich satisfy:UE_ID mod M<C

Clause 18. Infrastructure equipment for use with a wirelesstelecommunications network, the infrastructure equipment comprising:

-   -   a controller configured to generate a network characteristic        indicative of a network preference for biasing access to each of        a plurality of predetermined radio frequency resource by a        terminal device of the wireless telecommunications network, the        network characteristic determined for each predetermined radio        frequency resource being for use by the terminal device in        selecting one of the plurality of predetermined radio frequency        resources; and    -   a transceiver configured to:    -   transmit, to the terminal device, the generated network        characteristic indicative of the network preference for biasing        access to each of the plurality of predetermined radio frequency        resource by the terminal device ; and    -   exchange signals with the terminal device using the one of a        plurality of predetermined radio frequency resources.

Clause 19. A method of operating a terminal device for use with awireless telecommunications network, the method comprising:

-   -   determining a subset of a plurality of predetermined        radio'frequency resources on the basis of a network        characteristic indicative of a network preference for biasing        access to each predetermined radio frequency resource and an        operational characteristic associated with the terminal device;    -   selecting one of the plurality of predetermined radio frequency        resources from the determined subset; and    -   controlling a transceiver of the terminal device to exchange        signals with the wireless telecommunications network using the        selected one of the plurality of predetermined radio frequency        resources.

Clause 20. A method of operating infrastructure equipment for use with awireless telecommunications network, the method comprising:

-   -   generating a network characteristic indicative of a network        preference for biasing access to each of a plurality of        predetermined radio frequency resources by a terminal device of        the wireless telecommunications network, the network        characteristic determined for each predetermined radio frequency        resource being for use by the terminal device in selecting one        of the plurality of predetermined radio frequency resources; and    -   controlling a transceiver of the infrastructure equipment to:    -   transmit, to the terminal device, the generated network        characteristic indicative of the network preference for biasing        access to each of the plurality of predetermined radio frequency        resources by the terminal device; and    -   exchange signals with the terminal device using the selected one        of the plurality of predetermined radio frequency resources.

Clause 21. A wireless telecommunications system comprising a terminaldevice according to any one of clauses 1 to 17 and infrastructureequipment according to clause 18.

Clause 22. A terminal device for use with a wireless telecommunicationsnetwork, the terminal device comprising:

-   -   a transceiver configured to receive information indicative of        one or more access classes of terminal devices which are        permitted to exchange signals with the wireless        telecommunications network; and    -   a controller configured to update the received information to        modify the one or more access classes of terminal devices which        are permitted to exchange signals with the mobile        telecommunications network, the received information being        updated by the controller according to a predetermined function        of time.

Clause 23. A terminal device according to clause 22, wherein thecontroller is configured to control the transceiver to exchange signalswith the wireless telecommunications network at a particular time whenan access class of the terminal device matches one of the one or moreaccess classes of terminal devices which are permitted to exchangesignals with the wireless telecommunications network at that particulartime.

Clause 24. A terminal device according to clause 22, wherein thetransceiver is configured to receive at least one of the information andthe predetermined function of time via a system information broadcastmessage from the wireless telecommunications network.

Clause 25. A terminal device according to any one of clauses 22 to 24,wherein the controller is operable to periodically update the receivedinformation at a time period and in a manner specified by thepredetermined function of time.

Clause 26. A terminal device according to clause 25, wherein theinformation indicative of the one or more access classes of terminaldevices which are permitted to exchange signals with the wirelesstelecommunications network is a bitmap, wherein the position of each bitin the bitmap is indicative of a respective access class and the bit ateach position is indicative of whether or not that access class ispermitted to exchange signals with the wireless telecommunicationsnetwork.

Clause 27. A terminal device according to clause 26, wherein each updateof the bitmap comprises performing a shift operation on elements of thebitmap in accordance with a predetermined rule.

Clause 28. A terminal device according to clause 26, wherein each updateof the bitmap comprises defining the bitmap as one of a plurality ofpredetermined bitmaps.

Clause 29. A terminal device according to any one of clauses 22 to 28,wherein the possible updates of the information are consecutivelyapplied and periodically repeated.

Clause 30. A terminal device according to any one of clauses 22 to 29,wherein the time period at which the received information isperiodically updated is defined with reference to a time changingparameter associated with successive radio frames via which thetransceiver is configured to exchange signals with the wirelesstelecommunications network.

Clause 31. A terminal device according to clause 30, wherein the timechanging parameter is a system frame number (SFN) or Hyper-system framenumber (H-SFN) of successive radio frames.

Clause 32. A terminal device according to clause 31, wherein the timeperiod at which the received information is periodically updated isdefined by a predetermined number N of SFNs or H-SFNs.

Clause 33. A terminal device according to clause 32, wherein the updateto the information is applied when the following equation is satisfied:H-SFN Mod N=0

Clause 34. A terminal device according to clause 32, wherein there are Mpossible updates to the information indicative of the one or more accessclasses of terminal devices which are permitted to exchange signals withthe wireless telecommunications network, each possible update isassociated with a respective index value from 0 to M−1, and the updateof the information used to define the one or more access classes ofterminal devices which are permitted to exchange signals with thewireless telecommunications network for a given H-SFN is the update withindex:

$\left\lfloor \frac{H - {SFN}}{N} \right\rfloor{mod}\mspace{14mu} M$

Clause 35. A terminal device according to any one of clauses 22 to 34,wherein the terminal device is a Narrowband Internet of Things (NB-IoT)terminal device.

Clause 36. Infrastructure equipment for use with a wirelesstelecommunications network, the infrastructure equipment comprising:

-   -   a controller configured to generate information indicative of        one or more access classes of terminal devices which are        permitted to exchange signals with the wireless        telecommunications network and to generate a function of time        according to which a terminal device of the wireless        telecommunications network is configured to update the        information to modify the one or more access classes of terminal        devices which are permitted to exchange signals with the mobile        telecommunications network; and    -   a transceiver configured to transmit the generated information        and function of time to the terminal device.

Clause 37. A method of controlling a terminal device for use with awireless telecommunications network, the method comprising:

-   -   controlling a transceiver of the terminal device to receive        information indicative of one or more access classes of terminal        devices which are permitted to exchange signals with the        wireless telecommunications network; and    -   updating the received information to modify the one or more        access classes of terminal devices which are permitted to        exchange signals with the mobile telecommunications network, the        received information being updated by the controller according        to a predetermined function of time.

Clause 38. A method of controlling infrastructure equipment for use witha wireless telecommunications network, the method comprising:

-   -   generating information indicative of one or more access classes        of terminal devices which are permitted to exchange signals with        the wireless telecommunications network and generating a        function of time according to which a terminal device of the        wireless telecommunications network is configured to update the        information to modify the one or more access classes of terminal        devices which are permitted to exchange signals with the mobile        telecommunications network; and

controlling a transceiver of the infrastructure equipment to transmitthe generated information and function of time to the terminal device.

Clause 39. A wireless telecommunications system comprising a terminaldevice according to any one of clauses 22 to 35 and infrastructureequipment according to clause 36.

Numerous modifications and variations of the present disclosure arepossible in light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims, the disclosuremay be practiced otherwise than as specifically described herein.

In so far as embodiments of the disclosure have been described as beingimplemented, at least in part, by software-controlled data processingapparatus, it will be appreciated that a non-transitory machine-readablemedium carrying such software, such as an optical disk, a magnetic disk,semiconductor memory or the like, is also considered to represent anembodiment of the present disclosure.

It will be appreciated that the above description for clarity hasdescribed embodiments with reference to different functional units,circuitry and/or processors. However, it will be apparent that anysuitable distribution of functionality between different functionalunits, circuitry and/or processors may be used without detracting fromthe embodiments.

Described embodiments may be implemented in any suitable form includinghardware, software, firmware or any combination of these. Describedembodiments may optionally be implemented at least partly as computersoftware running on one or more data processors and/or digital signalprocessors. The elements and components of any embodiment may bephysically, functionally and logically implemented in any suitable way.Indeed the functionality may be implemented in a single unit, in aplurality of units or as part of other functional units. As such, thedisclosed embodiments may be implemented in a single unit or may bephysically and functionally distributed between different units,circuitry and/or processors.

Although the present disclosure has been described in connection withsome embodiments, it is not intended to be limited to the specific formset forth herein. Additionally, although a feature may appear to bedescribed in connection with particular embodiments, one skilled in theart would recognize that various features of the described embodimentsmay be combined in any manner suitable to implement the technique.

Annex 1:

The simplified structure of the downlink of an LTE wireless accessinterface presented in FIG. 2, also includes an illustration of eachsubframe 201, which comprises a control region 205 for the transmissionof control data, a data region 206 for the transmission of user data,reference signals 207 and synchronisation signals which are interspersedin the control and data regions in accordance with a predeterminedpattern. The control region 204 may contain a number of physicalchannels for the transmission of control data, such as a physicaldownlink control channel PDCCH, a physical control format indicatorchannel PCFICH and a physical HARQ indicator channel PHICH. The dataregion may contain a number of physical channel for the transmission ofdata, such as a physical downlink shared channel PDSCH and a physicalbroadcast channels PBCH. Although these physical channels provide a widerange of functionality to LTE systems, in terms of resource allocationand the present disclosure PDCCH and PDSCH are most relevant. Furtherinformation on the structure and functioning of the physical channels ofLTE systems can be found in [1].

Resources within the PDSCH may be allocated by an eNodeB to UEs beingserved by the eNodeB. For example, a number of resource blocks of thePDSCH may be allocated to a UE in order that it may receive data that ithas previously requested or data which is being pushed to it by theeNodeB, such as radio resource control RRC signalling. In FIG. 2, UE1has been allocated resources 208 of the data region 206, UE2 resources209 and UE resources 210. UEs in a an LTE system may be allocated afraction of the available resources of the PDSCH and therefore UEs arerequired to be informed of the location of their allocated resourceswithin the PDCSH so that only relevant data within the PDSCH is detectedand estimated. In order to inform the UEs of the location of theirallocated communications resources, resource control informationspecifying downlink resource allocations is conveyed across the PDCCH ina form termed downlink control information DCI, where resourceallocations for a PDSCH are communicated in a preceding PDCCH instancein the same subframe. During a resource allocation procedure, UEs thusmonitor the PDCCH for DCI addressed to them and once such a DCI isdetected, receive the DCI and detect and estimate the data from therelevant part of the PDSCH.

Each uplink subframe may include a plurality of different channels, forexample a physical uplink shared channel PUSCH 305, a physical uplinkcontrol channel PUCCH 306, and a physical random access channel PRACH.The physical Uplink Control Channel PUCCH may carry control informationsuch as ACK/NACK to the eNodeB for downlink transmissions, schedulingrequest indicators SRI for UEs wishing to be scheduled uplink resources,and feedback of downlink channel state information CSI for example. ThePUSCH may carry UE uplink data or some uplink control data. Resources ofthe PUSCH are granted via PDCCH, such a grant being typically triggeredby communicating to the network the amount of data ready to betransmitted in a buffer at the UE. The PRACH may be scheduled in any ofthe resources of an uplink frame in accordance with a one of a pluralityof PRACH patterns that may be signalled to UE in downlink signallingsuch as system information blocks. As well as physical uplink channels,uplink subframes may also include reference signals. For example,demodulation reference signals DMRS 307 and sounding reference signalsSRS 308 may be present in an uplink subframe where the DMRS occupy thefourth symbol of a slot in which PUSCH is transmitted and are used fordecoding of PUCCH and PUSCH data, and where SRS are used for uplinkchannel estimation at the eNodeB. Further information on the structureand functioning of the physical channels of LTE systems can be found in[1].

In an analogous manner to the resources of the PDSCH, resources of thePUSCH are required to be scheduled or granted by the serving eNodeB andthus if data is to be transmitted by a UE, resources of the PUSCH arerequired to be granted to the UE by the eNodeB B. At a UE, PUSCHresource allocation is achieved by the transmission of a schedulingrequest or a buffer status report to its serving eNodeB. The schedulingrequest may be made, when there is insufficient uplink resource for theUE to send a buffer status report, via the transmission of UplinkControl Information UCI on the PUCCH when there is no existing PUSCHallocation for the UE, or by transmission directly on the PUSCH whenthere is an existing PUSCH allocation for the UE. In response to ascheduling request, the eNodeB is configured to allocate a portion ofthe PUSCH resource to the requesting UE sufficient for transferring abuffer status report and then inform the UE of the buffer status reportresource allocation via a DCI in the PDCCH. Once or if the UE has PUSCHresource adequate to send a buffer status report, the buffer statusreport is sent to the eNodeB and gives the eNodeB information regardingthe amount of data in an uplink buffer or buffers at the UE. Afterreceiving the buffer status report, the eNodeB can allocate a portion ofthe PUSCH resources to the sending UE in order to transmit some of itsbuffered uplink data and then inform the UE of the resource allocationvia a DCI in the PDCCH. For example, presuming a UE has a connectionwith the eNodeB, the UE will first transmit a PUSCH resource request inthe PUCCH in the form of a UCI. The UE will then monitor the PDCCH foran appropriate DCI, extract the details of the PUSCH resourceallocation, and transmit uplink data, at first comprising a bufferstatus report, and/or later comprising a portion of the buffered data,in the allocated resources.

Although similar in structure to downlink subframes, uplink subframeshave a different control structure to downlink subframes, in particularthe upper 309 and lower 310 subcarriers/frequencies/resource blocks ofan uplink subframe are reserved for control signalling rather than theinitial symbols of a downlink subframe. Furthermore, although theresource allocation procedure for the downlink and uplink are relativelysimilar, the actual structure of the resources that may be allocated mayvary due to the different characteristics of the OFDM and SC-FDMinterfaces that are used in the downlink and uplink respectively. InOFDM each subcarrier is individually modulated and therefore it is notnecessary that frequency/subcarrier allocation are contiguous however,in SC-FDM subcarriers are modulation in combination and therefore ifefficient use of the available resources are to be made contiguousfrequency allocations for each UE are preferable.

As a result of the above described wireless interface structure andoperation, one or more UEs may communicate data to one another via acoordinating eNodeB, thus forming a conventional cellulartelecommunications system. Although cellular communications system suchas those based on the previously released LTE standards have beencommercially successful, a number of disadvantages are associated withsuch centralised systems. For example, if two UEs which are in closeproximity wish to communicate with each other, uplink and downlinkresources sufficient to convey the data are required. Consequently, twoportions of the system's resources are being used to convey a singleportion of data. A second disadvantage is that an eNodeB is required ifUEs, even when in close proximity, wish to communicate with one another.These limitations may be problematic when the system is experiencinghigh load or eNodeB coverage is not available, for instance in remoteareas or when eNodeBs are not functioning correctly. Overcoming theselimitations may increase both the capacity and efficiency of LTEnetworks but also lead to the creations of new revenue possibilities forLTE network operators.

REFERENCES

[1] LTE for UMTS: OFDMA and SC-FDMA Based Radio Access, Harris Holma andAntti Toskala, Wiley 2009, ISBN 978-0-470-99401-6.

[2] RP-151621, “New Work Item: NarrowBand IOT NB-IOT,” Qualcomm, RAN #69

[3] R1-157783, “Way Forward on NB-IoT,” CMCC, Vodafone, Ericsson,Huawei, HiSilicon, Deutsche Telekom, Mediatek, Qualcomm, Nokia Networks,Samsung, Intel, Neul, CATR, AT&T, NTT DOCOMO, ZTE, Telecom Italia, IITH,CEWiT, Reliance-Jio, CATT, u-blox, China Unicom, LG Electronics,Panasonic, Alcatel-Lucent, Alcatel-Lucent Shanghai Bell, China Telecom,RAN1 #83

[4] “Draft Report of 3GPP TSG RAN WG2 meeting #92”ftp://ftp.3gpp.org/tsg_ran/WG2_RL2/TSGR2_92/Report/R2-16xxxx_draft_report_RAN2_92_Anaheim_v0.1.zip

The invention claimed is:
 1. A terminal device for use with a wirelesstelecommunications network, the terminal device comprising: atransceiver configured to exchange signals with the wirelesstelecommunications network using one of a plurality of predeterminedradio frequency resources; and a controller configured to determine asubset of the plurality of predetermined radio frequency resources onthe basis of a network characteristic indicative of a network preferencefor biasing access to each predetermined radio frequency resource and anoperational characteristic associated with the terminal device, and toselect the one of the plurality of predetermined radio frequencyresources from the determined subset.
 2. The terminal device accordingto claim 1, wherein each of the plurality of predetermined radiofrequency resources is a Narrowband Internet of Things (NB-IoT) carrier.3. The terminal device according to claim 1, wherein: the networkcharacteristic indicative of the network preference for biasing accessto each predetermined radio frequency resource is a number of accessclasses of terminal devices which are permitted to exchange signals withthe wireless telecommunications network using that predetermined radiofrequency resource; the operational characteristic associated with theterminal device is an access class of the terminal device; and thecontroller is configured to include each predetermined radio frequencyresource via which terminal devices with the access class of theterminal device are permitted to exchange signals with the wirelesstelecommunications network in the subset of the plurality ofpredetermined radio frequency resources.
 4. The terminal deviceaccording to claim 3, wherein the controller is configured to select,from the predetermined radio frequency resources of the subset, thepredetermined radio frequency resource associated with the largestnumber of access classes of terminal devices which are permitted toexchange signals with the wireless telecommunications network using thatpredetermined radio frequency resource as the one of the plurality ofpredetermined radio frequency resources.
 5. The terminal deviceaccording to claim 1, wherein: the network characteristic indicative ofthe network preference for biasing access to each predetermined radiofrequency resource is a signal quality offset value associated with thatpredetermined radio frequency resource; the operational characteristicassociated with the terminal device is a signal quality measurementassociated with each predetermined radio frequency resource; and thecontroller is configured to include, in the subset of the plurality ofpredetermined radio frequency resources, each predetermined radiofrequency resource associated with a modified signal quality measurementwhich exceeds a predetermined threshold, the modified signal qualitymeasurement associated with each predetermined radio frequency resourcebeing given by the signal quality measurement associated with thatpredetermined frequency resource added to the signal quality offsetvalue associated with that predetermined radio frequency resource. 6.The terminal device according to claim 1, wherein: the networkcharacteristic indicative of the network preference for biasing accessto each predetermined radio frequency resource is a signal qualityoffset value associated with that predetermined radio frequencyresource; the operational characteristic associated with the terminaldevice is a signal quality measurement associated with eachpredetermined radio frequency resource; and the controller is configuredto include, in the subset of the plurality of predetermined radiofrequency resources, a predetermined radio frequency resource associatedwith a highest modified signal quality measurement, the modified signalquality measurement associated with each predetermined radio frequencyresource being given by the signal quality measurement associated withthat predetermined frequency resource added to the signal quality offsetvalue associated with that predetermined radio frequency resource. 7.The terminal device according to claim 5, wherein the calculation of thesignal quality offset value associated with each predetermined radiofrequency resource takes into account the effect of a signal qualityboosting value associated with that predetermined radio frequencyresource.
 8. The terminal device according to claim 5, wherein, for eachpredetermined radio frequency resource, the signal quality measurementis a Reference Signal Received Power (RSRP) measurement, the signalquality offset value is an RSRP offset value and the modified signalquality measurement is a modified RSRP measurement, wherein the RSRPoffset value serves to reduce the modified RSRP measurement relative tothe RSRP measurement for a predetermined radio frequency resource with alower level of network preference for biasing access to thatpredetermined radio frequency resource and to increase the modified RSRPmeasurement relative to the RSRP measurement for a predetermined radiofrequency resource with a higher level of network preference for biasingaccess to that predetermined radio frequency resource.
 9. The terminaldevice according claim 1, wherein: the network characteristic indicativeof the network preference for biasing access to each predetermined radiofrequency resource is an access class factor associated with thatpredetermined radio frequency resource, the access class factor being avalue within a predetermined range and being correlated with the levelof network preference for biasing access to that predetermined radiofrequency resource; the operational characteristic associated with theterminal device is a randomly generated value within the predeterminedrange; and the controller is configured to include, in the subset of theplurality of predetermined radio frequency resources, each predeterminedradio frequency resource which either: in the case that the access classfactor of each predetermined radio frequency resource is positivelycorrelated with the level of network preference for biasing access tothat radio frequency resource, has an access class factor greater thanthe randomly generated value of the terminal device; or in the case thatthe access class factor of each predetermined radio frequency resourceis negatively correlated with the level of network preference forbiasing access to that radio frequency resource, has an access classfactor less than the randomly generated value of the terminal device.10. The terminal device according to claim 9, wherein the predeterminedrange is from 0 to 1, and the access class factor is positivelycorrelated with the level of the network preference for biasing accessto each predetermined radio frequency resource.
 11. The terminal deviceaccording to claim 9, wherein the controller is configured to select,from the predetermined radio frequency resources of the subset, thepredetermined radio frequency resource associated with the access classfactor which is closest to the randomly generated value of the terminaldevice.
 12. The terminal device according to claim 1, wherein thecontroller is configured to select, from the predetermined radiofrequency resources of the subset, the predetermined radio frequencyresource associated with the highest signal strength or signal qualityas the one of the plurality of predetermined radio frequency resources.13. The terminal device according to claim 1, wherein the controller isconfigured to randomly select, from the predetermined radio frequencyresources of the subset, the one of the plurality of predetermined radiofrequency resources.
 14. The terminal device according to claim 1,wherein the controller is configured to select, from the predeterminedradio frequency resources of the subset, the one of the plurality ofpredetermined radio frequency resources based on an identifier, UE_ID,of the terminal device.
 15. The terminal device according to claim 14,wherein there are n predetermined radio frequency resources in thesubset and each predetermined radio frequency resource in the subset isassociated with one of a respective integer identifier from 0 to n−1,and the controller is configured to select as the one of the pluralityof predetermined radio frequency resources the predetermined radiofrequency resource with an identifier which is equal to UE-ID mod n. 16.The terminal device according to claim 14, wherein each predeterminedradio frequency resource in the subset is associated with a respectiveone or more of predetermined offset values and the controller isconfigured to select as the one of the plurality of predetermined radiofrequency resources a predetermined radio frequency resource associatedwith an offset value k_(i) which satisfies:(UE_ID+k _(i))mod M=C wherein M and C are predetermined values.
 17. Theterminal device according to claim 14, wherein each predetermined radiofrequency resource in the subset is associated with a respectivepredetermined value M and a respective predetermined value C, and thecontroller is configured to select as the one of the plurality ofpredetermined radio frequency resources a predetermined radio frequencyresource with respective predetermined values M and C which satisfy:UE_ID mod M<C.
 18. Infrastructure equipment for use with a wirelesstelecommunications network, the infrastructure equipment comprising: acontroller configured to generate a network characteristic indicative ofa network preference for biasing access to each of a plurality ofpredetermined radio frequency resources by a terminal device of thewireless telecommunications network, the network characteristicdetermined for each predetermined radio frequency resource being for useby the terminal device in selecting one of the plurality ofpredetermined radio frequency resources; and a transceiver configuredto: transmit, to the terminal device, the generated networkcharacteristic indicative of the network preference for biasing accessto each of the plurality of predetermined radio frequency resources bythe terminal device; and exchange signals with the terminal device usingthe one of a plurality of predetermined radio frequency resources.
 19. Amethod of operating a terminal device for use with a wirelesstelecommunications network, the method comprising: determining a subsetof a plurality of predetermined radio frequency resources on the basisof a network characteristic indicative of a network preference forbiasing access to each predetermined radio frequency resource and anoperational characteristic associated with the terminal device;selecting one of the plurality of predetermined radio frequencyresources from the determined subset; and controlling a transceiver ofthe terminal device to exchange signals with the wirelesstelecommunications network using the selected one of the plurality ofpredetermined radio frequency resources.